BRPI1002970B1 - process for the production of hydrogen from ethanol - Google Patents

Abstract

PROCESS FOR THE PRODUCTION OF HYDROGEN FROM ETHANOL. The process described in the present invention produces a gas rich in methane and hydrogen and with a content of less than 1% v / v olefins, which fully satisfies the requirements for the raw materials used to produce hydrogen or synthesis gas in large quantities. scale, in steam reforming units that already exist in a large number of oil refineries and petrochemical units. From ethanol, water vapor, nickel-based catalysts and the use of suitable temperature ratios, molar ratios H20 / ethanol and H2 / ethanol, the invention teaches the production of hydrogen and synthesis gas from biomass, stable way for long periods without loss of performance of the catalysts over time, allowing its industrial application in new units or in existing units. As a solution for the production of ethanol, the present invention claims the replacement of the ZnO-based catalysts and hydrotreating of the pre-treatment section of the load, with nickel-based catalysts and process conditions in accordance with the present invention.

Description

FIELD OF THE INVENTION

The present invention belongs to the field of catalytic steam reforming processes and the catalysts used in these processes. The production of hydrogen from biomass, in particular ethanol, is of great interest for new industrial units and fuel cells and is the objective of the present invention.

BACKGROUND OF THE INVENTION

The most used process for the production of hydrogen on an industrial scale is steam reforming. It is a multi-stage process with different operating conditions and catalysts. In the stage called “steam reform”, which uses a nickel-type catalyst on refractory supports, such as alumina, calcium aluminate or magnesium aluminate, the main reactions that occur are:

The steam reform process uses natural gas, refinery gas, propane, butane, liquefied petroleum gas or naphtha as raw materials.

The use of renewable raw materials (biomass) for the production of hydrogen, such as ethanol, would make it possible to reduce CO2 emissions in the global balance, since these raw materials fix CO2 from the atmosphere. Despite the environmental benefit, the technology for producing H2 on a large scale from ethanol is not yet technically consolidated.

The deactivation of the catalysts used in the steam reform process by the formation of coke is the main difficulty to be solved, for the industrial viability of the production of hydrogen from ethanol.

The ethylene formed from ethanol dehydration is one of the main compounds that favor the formation of coke in the ethanol steam reform. In an industrial steam reforming unit using natural gas or refinery gas, the maximum permissible ethylene content in the feed is considered to be around 1% v / v. Above this value, the loss of catalyst activity makes the process economically unfeasible.

A technical solution that has been investigated is the development of catalysts that are more resistant to deactivation by coke deposition. Some of the types of catalysts investigated are: oxides and mixed oxides such as MgO, AI2O3, V2O5, ZnO, TiO2, l_a2O3, CeO2, Sm2O3, La2O3-AI2O3, CeO2-AI2O3, MgO-AI2O3; Co supported as CO / AI2O3, Co / l_a2O3, Co / SiO2, Co / MgO, Co / ZrO2, Co / ZnO, Co / TiO2) Co / V2O5, Co / CeO2, Co / Sm2O3, Co / CeO2-ZrO2, Co /Ç; Ni supported as Ni / La2O3 Ni (La2O3-AI2O3), Ni / AI2O3, Ni / MgO, Ni-Cu / SiO2) Ni-Cu / AI2O3, Ni-Cu-K / AI2O3; CU supported on Nb2O5-AI2O3 and on ZnO-AI2O3; noble metals supported as Rh on TiO2, SiO2, CeO2, ZrO2, AI2O3, MgO and CeO2-ZrO2, Pt on CeO2, Pd on CeO2, AI2O3 and C; metal alloys such as Rh-Au / CeO2, Rh-Pt / CeO2 and Pt-Pd / CeO2.

However, such catalysts still have restrictions for industrial use, such as: not having adequate resistance to deactivation by coke formation or sintering of the active phase; present high cost because they are based on noble metals or form by-products, such as acetaldehyde, acetates, acetone and ethylene, which hinder the purification of the hydrogen (or synthesis gas) produced or cause difficulties and / or additional costs due to condensate contamination generated in the process from the water used in excess in the reaction stoichiometry.

A second technical solution, and scope of the present invention, would be the prior conversion of ethanol into raw materials used industrially, which converts ethanol into a gas rich in methane and free from olefins and other organic contaminants, such as acetaldehydes, ketones, acetates and others, through the combination of process conditions and suitable catalysts that have low coke formation. Such gas can then be used as a charge in a conventional hydrogen production unit that uses natural gas, LPG, refinery gas, naphtha or combinations of these, as raw materials.

The production of hydrogen by steam reforming of ethanol can be described theoretically by the global equation below:

b) a formação de acetaldeído pela desidrogenação do etanol.

c) a decomposição do etanol e a reação de reforma a vapor do etanol ou de produtos intermediários produzindo CO, CO2 e CH4.

In practice, several other reactions may occur, depending on the type of catalyst and the operating conditions used, such as: a) the formation of ethylene by the ethanol dehydration reaction.

b) the formation of acetaldehyde by the dehydrogenation of ethanol.

c) the decomposition of ethanol and the steam reforming reaction of ethanol or intermediate products producing CO, CO2 and CH4.

Noble metal-containing catalysts tend to have greater resistance to coke formation than equivalent catalysts using nickel as the active phase. However, producing them requires higher costs, which tends to make their industrial use unfeasible. Thus, despite being known for a long time, such noble metal-based catalysts have found no industrial application in large-scale hydrogen production.

Industrially, the catalysts used for the production of hydrogen from natural gas, propane, butane, LPG, refinery gas or naphtha, in large capacity units (defined here as having a production capacity above 10,000 Nm3 / day), comprise nickel supported on refractory materials, such as: alumina, calcium aluminate or magnesium aluminate, which can be promoted by other elements, such as alkali metals (especially potassium) and rare earths (especially lanthanum).

Nickel-based catalysts can be severely deactivated by coke formation when used for steam reforming of ethanol, the rate of coke formation being influenced by the type of catalyst and the operating conditions.

The Ni / AI2O3 type catalyst has good activity and selectivity for hydrogen production at temperatures above 550 ° C. At lower temperatures, the appearance of ethylene in the products is observed, accompanied by a rapid loss of activity associated with the deposition of coke.

The trend towards the formation of coke on supported nickel catalysts in the ethanol steam reform is well known. Sun and colleagues report in the publications J. Sun, X.P. Qiu, F. Wu, W.T. Zhu, HH2 from steam reforming of ethanol at low temperature over NÍ / Y2O3, Ni / La2O3 and NI / AI2O3 catalysts for fuel-celf ', International Journal of Hydrogen Energy 30 (2005) 437-445 and J. Sun, X. Qiu , F. Wu, W. Zhu, W. Wang, S. Hao, “Hydrogen from steam reforming of ethanol in low and middle temperature range for fuel cell application”, International Journal of Hydrogen Energy 29 (2004) 1075-1081 who used catalysts of the type NÍ / Y2O3, Ni / La2O3 and Ni / AI2O3. The authors taught that the use of substrates that do not have acidity, at temperatures above 380 ° C, reduces the formation of coke.

The invention described in patent document WO 2009/004462 A1, teaches how to produce hydrogen and carbon nanotubes (a special type of coke) from the decomposition of ethanol on nickel-based catalysts supported on lanthanum.

The results released show that the performance of nickel-based catalysts, for the production of hydrogen from ethanol, is applicable to existing hydrogen production units, but can still be improved. One technique described in the literature for the production of hydrogen from ethanol, called autothermal reform, involves adding oxygen to the mixture of ethanol and steam.

The publication WO 2009/009844 A2 teaches the addition of oxygen to the ethanol and water vapor feed, associated with the use of specific catalysts, based on cerium oxide, with promoters selected from the group of alkali metals and lanthanides, for the production of H2 from ethanol.

Another example of this technique is the invention described in US patent document 2005/0260123 A1, which teaches a process to produce hydrogen, which uses catalysts that comprise Rh on supports, such as cerium oxide, and is conducted in autothermal conditions with introduction of oxygen in the reaction gas.

The use of oxygen in food, although it presents advantages; how to provide the reaction heat through combustion reactions, and assist in removing the coke formed on the catalyst, is not a practical method for large-scale hydrogen production, due to the associated cost of oxygen production and hydrogen purification, when using air instead of oxygen. Such a method would hardly be applied in existing industrial hydrogen production units by steam reform, due to the high investments required to change the equipment.

Conceptually, a possible technique to be applied to the production of hydrogen from ethanol would be its previous conversion into raw materials, which are already used industrially for the production of hydrogen on a large scale, such as naphtha, natural gas or hydrocarbons. such as methane, ethane, propane and butane. After a first stage of previous conversion of ethanol, the hydrocarbon stream would feed the conventional hydrogen production process that already exists industrially, where the hydrocarbons would be converted to the mixture of H2, CO, CO2 and residual methane. In the final part of the process, the H2 (or if the H2 / CO mixture is desired) would be purified by conventional amine absorption techniques or via PSA (“pressure swing adsorption”).

The patent document US 2006/0057058 A1 teaches a method for the production of a gas rich in hydrogen from ethanol characterized by: a) a first stage where ethanol, water vapor and recycle hydrogen feed a reactor, where they occur the catalytic steps of dehydrogenation from ethanol to ethylene and hydrogenation from ethylene to ethane (the catalyst comprises Pt, Pd or Cu on a support selected from the group alumina, silica-alumina, zirconia and zeolites, particularly HZSM5 zeolite); b) a second stage of adiabatic pre-reform where the stream rich in ethane is transformed into a stream rich in methane; c) supply of methane-rich current in a typical configuration of industrial steam reforming units, containing a primary reformer and a shift reactor.

The invention does not report data on the stability of the catalysts. The hydrogen produced in accordance with this invention supplies a fuel cell and is therefore suitable for use on a small scale.

Patent document WO / 2009/130197 reports a method for converting ethanol to methane in a pre-reformer. According to the method, ethanol and water vapor are put to react on a catalyst that comprises platinum on a support of ZrO2 and CeO2, in the temperature range between 300 ° C and 550 ° C.

In S. Freni, N. Mondelo, S. Cavallaro et al., React. Kinet. Catai. Lett, 71 (2000) 143, reports the use of a first stage of conversion of ethanol to acetaldehyde, in the presence of steam and hydrogen, on a Cu-type catalyst supported on silica, at temperatures between 300 ° C and 400 ° C and then the steam reforming reaction of the reaction mixture over a Ni-type catalyst supported on magnesium oxide.

The specialized literature also presents several citations and descriptions of processes in two stages for the production of hydrogen from ethanol. Such processes, however, have the drawbacks of using catalysts based on noble metals or producing intermediate compounds, of which there is no experience of the impact they have on the performance of the catalysts used industrially, in the steam reforming stage, being necessary the accomplishment tests to prove the durability of catalytic systems and their applicability in existing units.

SUMMARY OF THE INVENTION

The present invention concerns a process for producing hydrogen from ethanol and a specific catalytic system for use in said process. An essential feature of the present invention is the conversion of ethanol, in a first stage of the process, into a gas rich in methane, free of olefins (<1%), with low levels of carbon monoxide (<2%) and other organic contaminants , such as acetaldehyde.

The present invention can be implemented in large scale industrial hydrogen production units, with replacement of the catalysts in the pretreatment section (usually ZnO and CoMo) and use of the process conditions described therein.

DETAILED DESCRIPTION OF THE INVENTION

The present invention concerns a process for producing hydrogen from ethanol and the use, in said process, of specific nickel-based catalysts. The process of producing hydrogen from ethanol is characterized by comprising two stages, which actually result from the combination of two processes performed in series.

In the first stage, a pre-reform process comprises reactions that produce a gas with a high methane content and, in the second stage, a typical configuration of the steam reforming process used industrially is adequate to receive the product generated in the first stage. Therefore, the present invention can be implemented in existing hydrogen production units by replacing the catalysts in the pre-treatment section or in the pre-reform section with suitable catalysts and appropriate process conditions for carrying out the first stage. , in accordance with the present invention.

In the first stage, ethanol, in the presence of hydrogen with molar H2 / ethanol ratios between 0.1 mol / mol and 1.0 mol / mol, preferably between 0.2 mol / mol and 0.6 mol / mol, water vapor with molar ratios H2O / ethanol between 1 mol / mol and 10 mol / mol, temperatures between 300 ° C and 550 ° C, preferably between 350 ° C and 450 ° C and spatial speeds (LHSV considering only ethanol) between 0.1 h'1 and 10 h'1, preferably between 0.5 h'1 and 3 h'1, is converted in the presence of a nickel-based catalyst into a gas with a high content of methane, free from olefins and with low carbon monoxide content (less than 2% v / v of this component on a dry basis).

The operating pressure can be used in the industrial practice of the steam reform process, that is, due to the state of the art between 1 kgf / cm2 and 40 kgf / cm2, preferably between 10 kgf / cm2 and 25kgf / cm2, the maximum value defined by the limitations of the construction materials of the industrial unit.

In the second stage, gas with a high methane content is used as a charge in a hydrogen production unit by the steam reform process. A typical configuration of the steam reform process, used industrially and suitable to receive the gas with a high methane content generated in the first stage, comprises the following additional steps: a) primary reform, where the mixture between water vapor and high gas methane content is converted into a mixture, with high levels of H2, CO and CO2 and low methane content, and the reaction temperatures are in the range between 500 ° C and 850 ° C and pressures between 10 kgf / cm2 and 40 kgf / cm2; b) "shift", where CO reacts with water vapor at temperatures between 300 ° C and 450 ° C and pressures between 10 kgf / cm2 and 40 kgf / cm2; c) purification, where through the use of the "pressurize" technique swing adsorption ”produces a current with a purity greater than 99% hydrogen and a residual gas containing H2, CO, CO2 and methane, which is used as a fuel in the primary reform stage.

Other steam reform process configurations known in industrial practice can be used to process gas with a high methane content generated in the first step of the process, such as process configurations containing pre-reform, secondary reform, shift reactors ”Medium (MTS), low shift (LTS) and methanation and purification of hydrogen-rich gas through the use of aqueous amine solutions. Steam reformulation process configurations for synthesis gas production can also be used, as currents containing in addition to hydrogen, significant CO levels for use in petrochemical processes such as methanol production or in Fischer Tropsch processes.

The catalysts of the present invention comprise nickel on a low acid inorganic support, selected from zinc oxide, calcium titanate and calcium or magnesium aluminate, or a mixture of these, the support being able to be modified by alkali metals, particularly by adding potassium, to reach a content between 0.1% w / w and 10% w / w, preferably between 1% to 5% potassium.

The process of preparing the nickel-based catalyst supported on inorganic oxides for use in the process claimed by the present invention comprises the following steps: 1) preparation of a solution of an inorganic nickel salt, preferably nitrate, acetate or carbonate, which may contain a or more elements from the group of lanthanides (or rare earths), preferably lanthanum or cerium; 2) impregnation of the inorganic oxide support by known techniques of pore volume (wet spot) or by the excess solution method; 3) drying of the inorganic oxide material impregnated with a solution containing nickel in air, at temperatures between 80 ° C and 140 ° C, for 1 to 24 hours; 4) calcination of inorganic oxide material impregnated in air, between 350 ° C and 650 ° C, for 1 to 4 hours.

Alternatively, steps 2 to 4 can be repeated more than once until the desired NiO content in the support is achieved. The desired levels are between 10% w / w and 40% w / w of NiO, preferably between 12% and 20%. In addition, compounds for pH control, increased solubility or to avoid phase precipitation may be included as additives in the impregnation. Non-limiting examples of these compounds are nitric acid, sulfuric acid, phosphoric acid, ammonium hydroxide, ammonium carbonate, hydrogen peroxide (H2O2), sugars or combinations of these compounds. Optionally, in the preparation of the support an alumina content between 5% and 50% is added, to obtain a mechanical resistance of the catalysts suitable for industrial use. The support particles can be in various forms suitable for industrial use in the steam reforming process, such as spheres, cylinders, cylinders with a central hole ("Rashing" rings) and cylinders with several holes.

The nickel oxide catalysts on the support require transformation to the active phase of metallic nickel on the support. The transformation, called reduction, can be carried out before feeding ethanol and water vapor, through the passage of a flow of hydrogen or a reducing agent such as ammonia, methanol or acetaldehyde, under temperature conditions between 300 ° C and 550 ° C. Optionally, the catalyst can be reduced externally, as a final step in its production process, by passing a flow of hydrogen or a reducing agent such as ammonia, methanol or acetaldehyde, under temperature conditions between 300 ° C to 550 ° C, for 1 to 5 hours, and then cooled and subjected to an air flow at temperatures between 20 ° C and 60 ° C, for 1 to 5 hours. Optionally, the catalysts can contain low levels of noble metals, particularly Pd and Pt at levels below 0.5% w / w, or preferably below 0.1% w / w, to accelerate the reduction step.

The catalysts, thus prepared, can be used in the production of a gas with a high methane content, olefin content less than 1% w / w and low CO content, at pressures between 1 kgf / cm and 50 kgf / cm and temperatures between 300 ° C and 550 ° C, from the mixture of ethanol, hydrogen and water vapor with molar ratios H2 / ethanol between 0.2 mol / mol and 0.6 mol / mol and molar H2O / ethanol ratios between 1 mol / mol and 10 mol / mol, which allow to operate for long periods without loss of performance due to coke formation. Gas with a high methane content can be used for hydrogen production through the steam reforming process.

The present invention also optionally provides for the use of commercial catalysts classified as "methanation" or catalysts classified as "pre-reform", both based on nickel, as long as used in the process conditions taught. The following examples are presented in order to more fully illustrate the nature of the present invention and the way to practice it, without, however, being considered as limiting its content.

EXAMPLES Example 1

This example, comparing the state of the art, teaches that commercial zinc oxide adsorbents and commercial hydrotreating catalysts containing cobalt and molybdenum, both used industrially in the steam reforming process in the pre-treatment process filler step steam reform, are not suitable 10 for processing an ethanol and hydrogen feed, since they have a high rate of formation of ethylene and other by-products, particularly acetaldehyde, even when a high molar ratio H2 / ethanol is used in the feed (Table 1). Table 1 15 Distribution of hydrocarbons in the gas phase obtained in the conversion of ethanol in the presence of hydrogen over zinc oxide adsorbents and hydrotreating catalysts used in the industrial steam reforming process.

Such by-products are not desirable because they provide early deactivation of the catalyst used or steam reforming catalysts, used later in the process.

The results were obtained in a microactivity unit 5 operating at atmospheric pressure.

The catalysts were ground for the range between 100 mesh and 150 mesh. Ethanol was fed through the passage of the carrier gas (hydrogen or nitrogen) through a saturator maintained at 10 ° C.

The analyzes of the charge and the product formed were performed by means of gas chromatography.

Example 2

This comparative example teaches that commercial zinc oxide adsorbents and hydrotreating catalysts containing cobalt and molybdenum, which are used in the pre-treatment of fillers in the industrial steam reforming process, are not suitable for processing a feeding of ethanol, hydrogen and water vapor, under temperature conditions industrially used in the pretreatment reactors, since they lead to a high rate of formation of ethylene and other by-products, particularly acetaldehyde and light olefins.

This example further illustrates the beneficial effect of the presence of water vapor (comparison between Examples 2.1 and 2.2) and reduced spatial velocity (comparison between Examples 2.4 and 2.5) in reducing the formation of ethylene and other light olefins.

The catalysts were tested using procedures similar to those described in Example 1.

The present invention claims to replace the ZnO-based catalysts and the hydrotreating of the pre-treatment section of the load, with nickel-based catalysts, prepared according to the present invention as a solution for the production of ethanol in a reforming units a existing steam. Table 2

Distribution of hydrocarbons in the gas phase obtained in the conversion of ethanol in the presence of hydrogen and water vapor over zinc oxides and hydrotreating catalysts, both commercial (Oxiteno), used in the industrial process of steam reform.

Example 3

This comparative example, in accordance with the present invention, teaches the use of a support of the zinc oxide type, for the preparation of a nickel oxide based catalyst and its use in the production of hydrogen from ethanol. The following samples were prepared:

Sample 3A: 95 grams of commercial adsorbent based on zinc oxide (ZINOX390) were impregnated, by the incipient impregnation method, with 38 ml of aqueous solution containing 19.5 grams of Ni (NO3) 2 6H2O. Then, the sample was dried at 110 ° C 10 for one night and calcined at 450 ° C in air for 4 hours in order to obtain 5% w / w of NiO supported on zinc oxide;

Sample 3B: 94 grams of the catalyst of Example 5 were impregnated, by the incipient impregnation method, with 40 ml of aqueous solution containing 21.4 grams of Ni (NO3) 2 6H2O. Then, the sample was dried at 110 ° C for one night and calcined at 450 ° C in air for 4 hours in order to obtain 10% w / w of NiO supported on zinc oxide;

Sample 3C: 95 grams of the catalyst of Example 6 were impregnated, by the incipient impregnation method, with 40 ml of aqueous solution containing 21.7 grams of Ni (NO3) 2 6H2O nickel nitrate. Then, the sample was dried at 110 ° C for one night and calcined at 450 ° C in air for 4 hours in order to obtain 15% w / w of NiO supported on zinc oxide.

Example 4

This comparative example, in accordance with the present invention, teaches the use of a support of the type of zinc oxide promoted by alkali metals, for the preparation of a catalyst based on nickel oxide and its use in the production of hydrogen from ethanol .

Initially, a support of zinc oxide promoted by potassium was prepared, as follows: 150 grams of commercial adsorbent based on zinc oxide (ZINOX390) were impregnated with 60 ml of aqueous solution containing 3.1 grams of hydroxide of potassium; then, the sample was dried at 110 ° C for one night and calcined at 450 ° C for 4 hours, to obtain 2% K2O over zinc oxide. Several catalysts containing nickel oxide were then prepared from this support, as described below:

Sample 4A: 95 grams of the material prepared in Example 8 were impregnated, by the incipient impregnation method, with 28 ml of aqueous solution containing 19.5 grams of Ni (NO3) 2 6H2O. Then, the sample was dried at 110 ° C for one night and calcined at 450 ° C in air for 4 hours, to obtain 5% w / w of NiO supported on zinc oxide promoted by potassium.

Sample 4B: 87 grams of the catalyst of Example 8 were impregnated, by the incipient impregnation method, with 37 ml of aqueous solution containing 19.9 grams of nickel nitrate Ni (NO3) 2 6H2O. Then, the sample was dried at 110 ° C for one night and calcined at 450 ° C in air for 4 hours, to obtain 10% w / w of NiO supported on zinc oxide promoted by potassium.

Sample 4C: 79 grams of the catalyst of Example 8 were impregnated, by the incipient impregnation method, with 26 ml of aqueous solution containing 20.2 grams of Ni (NO3) 2 6H2O nickel nitrate. Then, the sample was dried at 110 ° C for one night and calcined at 450 ° C in air for 4 hours, to obtain 15% w / w of NiO supported on zinc oxide promoted by potassium.

Example 5

The catalysts prepared in Examples 3 and 4 were previously reduced in hydrogen flow and water vapor at 450 ° C for 2 hours and then tested in a similar manner to that described in Example 1.

The results are presented in Table 3 and show that: a) the introduction of nickel oxide in the formulation of a zinc oxide type support produces a catalyst, which favors the reduction of by-product molecules, especially ethylene and acetaldehyde, and additional advantage is the increase in ethanol conversion activity; b) the introduction of potassium in the catalyst based on nickel oxide on zinc oxide leads to a further reduction in the content of ethylene and other olefins, which are the main compounds that accelerate the formation of coke in the conditions of conversion of ethanol to gas of synthesis.

EXAMPLE 6

This comparative example demonstrates that commercial steam reforming catalysts for natural gas and naphtha have high deactivation, shown by the sharp drop in conversion in Table 4, when used for steam reforming of ethanol in the presence of hydrogen and under existing temperature conditions in the pretreatment section of existing hydrogen generation units. 5 The catalysts were previously reduced in hydrogen flow and water vapor at 450 ° C for 2 hours and then tested in a similar way to that reported in Example 1. Table 3

Tabela 4Distribution of hydrocarbons in the gas phase obtained in the conversion 10 of ethanol in the presence of hydrogen and water vapor. Vapor / ethanol molar ratio = 2.8 mol / mol, H2 / ethanol molar ratio = 250 mol / mol, GHSV = 23000 l / gh, temperature of 400 ° C and pressure of 1 atm.

Table 4

Distribution of hydrocarbons in the gas phase obtained in the conversion of ethanol in the presence of hydrogen and water vapor over commercial steam reforming catalysts of natural gas (G91EW) or naphtha (46.3Q) 5 used in the industrial process of steam reforming. Vapor / ethanol molar ratio = 2.8 mol / mol and H2 / ethanol molar ratio = 250 mol / mol.

Example 7

This example shows that commercial catalysts known in industrial practice as methanation catalysts, originally used in the conversion of carbon monoxide and carbon dioxide to hydrogen, for the production of methane, can surprisingly be used, according to the present invention, for the conversion of ethanol into a gas rich in methane and free from olefins, in the presence of hydrogen and water vapor and in the temperature conditions used in the pretreatment section of existing hydrogen generation units by the steam reform process.

The catalysts were previously reduced in hydrogen flow 5 and water vapor at 450 ° C for 2 hours and then tested in a similar way to that described in Example 1. However, the activity and deactivation properties were shown to be influenced by type of commercial catalyst used, indicating that it would be desirable to prepare specific catalysts for the conversion of ethanol to hydrogen, in accordance with that proposed in the present invention. Table 5

Distribution of hydrocarbons in the gas phase obtained in the conversion of ethanol in the presence of hydrogen and water vapor over commercial methanation catalysts. Vapor / ethanol molar ratio = 2.8 mol / mol and 15 H2 / ethanol molar ratio = 250 mol / mol.

Example 8

This example teaches the preparation of a catalyst, according to the present invention, based on nickel on alumina type support and promoted by alkali metals. 300 grams of commercial aluminum hydroxide (PURAL SB, marketed by SASOL) were impregnated with 180 ml of aqueous solution containing 7.1 grams of potassium hydroxide. Then, the sample was dried at 110 ° C for 12 hours and calcined in air at 1200 ° C, for 4 hours, to obtain an alumina-type support promoted by potassium. Then, the sample was impregnated by the incipient impregnation method, with an aqueous solution containing nickel nitrate, dried at 110 ° C and calcined at 450 ° C. The procedure was repeated two more times in order to obtain a catalyst containing 15% NiO (15% NiO / 2% K / alumina).

Example 9

This example teaches the preparation of a catalyst, according to the present invention, based on nickel on magnesium aluminate type support and promoted by alkali metals. Initially, a magnesium aluminate type support was prepared from the following steps: a) mix an aqueous solution of AI (NO3) 3 9H20 with an aqueous solution of Mg (NO3) 2 6H2O, at room temperature; b) add the previous solution over an aqueous solution containing 14.5% NH4OH, keeping the pH equal to or above 8.0; c) filter and wash the precipitate formed with demineralized water; d) dry at 110 ° C and calcine in air between 1000 ° C and 1300 ° C for 1 to 4 hours (in the example, the solutions contain 543 grams of aluminum nitrate in 1435 ml of water and 176 grams of magnesium nitrate in 679 ml of water, respectively).

The used calcination temperature was 1100 ° C. The prepared support was then impregnated to the pore volume with aqueous KOH solution and then calcined at 1200 ° C, for 4 hours, in order to obtain a support with 1.5% w / w KOH. Then, 112 grams of the support thus obtained were impregnated with 39 ml of an aqueous solution containing 23 grams of Ni (NO3) 2 6H2O. The material was dried and calcined at 450 ° C for 4 hours to obtain 5% NiO supported on magnesium aluminate promoted by potassium. The procedure was repeated until 15% of NiO supported on potassium-promoted magnesium aluminate was obtained.

Example 10

This example teaches the preparation of a catalyst, according to the present invention, based on nickel on a calcium aluminate type support and promoted by alkali metals. 300 grams of commercial calcium aluminate (SECAR 80) were impregnated to the pore volume with an aqueous solution of KOH and then calcined at 1200 ° C for 4 hours to obtain a support of promoted calcium aluminate. by 1.5% w / w KOH. 114 grams of the support thus obtained were impregnated with 31 ml of an aqueous solution containing 23 grams of Ni (NO3) 2 6H2O. The material was dried and calcined at 450 ° C for 4 hours to obtain 5% NiO supported on calcium aluminate promoted by potassium. The procedure was repeated until 15% of NiO supported on potassium-promoted calcium aluminate was obtained.

Example 11

This example teaches the preparation of a catalyst, according to the present invention, in its preferred modality, based on nickel on supports of the type of alkali metal titanates. 190 grams of commercial calcium titanate (Certronic) are impregnated with 68 ml of an aqueous solution containing 39 grams of Ni (NO3) 2 6H2O. Then, the sample was dried at 110 ° C for one night and calcined at 450 ° C in air for 4 hours in order to obtain 5% w / w of NiO supported on calcium titanate. The procedure was repeated two more times in order to obtain the catalyst containing 15% w / w of NiO supported on calcium titanate.

Example 12

This example teaches the preparation of a catalyst, according to the present invention, based on nickel on an alumina-calcium type support. 235 grams of CATAPAL alumina were impregnated with 141 ml of aqueous solution containing 63 grams of Ca (NO3) 2 4H2O. Then, the sample was dried at 110 ° C for 1 night and calcined at 600 ° C for 4 hours in the air. 230 grams of the above support were impregnated to the pore volume with 160 ml of aqueous solution containing 99.4 grams of Ni (NO3) 2 6H2O. Then, the sample was dried at 110 ° C for one night and calcined at 450 ° C in air for 4 hours in order to obtain 10% w / w of NiO supported on alumina. The impregnation and calcination procedure was repeated in order to obtain the final catalyst containing 20% NiO supported on calcium modified alumina.

Example 13

This comparative example (Table 6) demonstrates that preferred catalysts of the present invention, made of nickel on low acid supports, have high stability and selectivity, for the production of a gas with a high methane content and free of olefins, under existing temperature conditions. in the pretreatment section of existing hydrogen generation units. The catalysts were previously reduced in hydrogen flow and water vapor at 450 ° C for 2 hours and then tested in a similar manner as described in Example 1. Table 6

Distribution of hydrocarbons in the gaseous phase obtained in the conversion of ethanol in the presence of hydrogen and water vapor on catalysts made of nickel on low acid supports.

The results show that an active, stable and selective catalyst for methane production can be obtained from the mixture of ethanol, hydrogen and water vapor.

The catalyst, according to the present invention, consists of Ni on alumina-type supports, calcium aluminates, magnesium aluminates and calcium titanates, which can be promoted by alkali metals, such as potassium.

Example 14

This example shows that, according to the present invention, the use of hydrogen, with molar ratios between 0.1 mol / mol and 1.0 mol / mol in the ethanol and water vapor mixture, is essential to avoid the formation of coke . In practice, a typical molar ratio between 0.01 mol / mol and 0.05 mol / mol is used industrially in the steam reform of natural gas and between 0.1 mol / mol to 0.3 mol / mol for the reform steam from naphtha. The reaction is carried out in a bench unit using 2 grams of catalyst, pressure of 10 kgf / cm2, temperature of 400 ° C, 30% w / w solution of ethanol in water (corresponding to a molar vapor / carbon ratio of 3.0 mol / mol), LHSV = 9h'1 (calculated based on the mixture of ethanol and water).

Tables 7 and 8 show the results obtained with commercial pre-reform and methanation catalysts, respectively, which are typically used in the production of hydrogen by the steam reform process. Pre-reform and methanation catalysts are used in the production stages of a gas with a high H2 content, from natural gas, LPG or naphtha. 5 Table 7

Stability test of the conversion of ethanol and water vapor to a gas with a high methane content as a function of the molar ratio H2 / ethanol on commercial pre-reform catalysts. The RKNGR catalyst was reduced to 450 ° C and the Reformax catalyst to 550 ° C before the reaction started.

Example 15

This example shows the use of catalysts, according to the present invention, in their preferred modality, of the Ni type on low acid supports. The reaction conditions were described in Example 5. The results show excellent stability without increasing pressure drop, indicative of coke formation on the catalysts (Table 9). Table 8

Tabela 9Stability test of conversion of ethanol and water vapor to a gas with a high methane content as a function of the molar ratio H2 / ethanol on commercial catalysts (C13-4-04 Sud Chemie) of methanation.

Table 9

Stability test of Ni-based catalysts on low acid supports in the conversion of ethanol and water vapor to a gas with a high methane content. The catalysts were reduced to 450 ° C before the reaction started.

Claims (9)

1- PROCESS FOR THE PRODUCTION OF HYDROGEN FROM ETHANOL, characterized by comprising the following steps: a) providing the reactor with a catalytic system where the said catalytic system comprises a nickel oxide catalyst on a support with a content comprised in the range between 10% w / w and 40% w / w, selected from the group alumina, calcium aluminate and magnesium aluminate or mixture of these compounds, in any proportion, and with a promoter element selected from the group of alkaline or alkaline earth metals, in which said alkali metal promoting element comprising potassium, present in the catalyst with a content in the range between 0.5% w / w and 5% w / w; b) provide this reactor with an ethanol feed load, with a spatial speed (LHSV) between 0.5 tr1 and 3.0 tr1 and allow contact with the catalytic system; c) provide this reactor simultaneously with steps (a) and (b) with a hydrogen supply, to establish a molar ratio H2 / ethanol (mol / mol) between 0.2 and 0.6; d) provide said reactor simultaneously with steps (a), (b) and (c) with a water vapor supply, to establish a water vapor / ethanol (mol / mol) molar ratio between 3 , 0 and 6.0; e) adjust the operating conditions of the reactor to a temperature between 350 ° C and 550 ° C; f) allow the conversion of ethanol and a stream containing methane, CO, CO2 and H2, under the conditions established in the previous steps; g) direct the gas mixture produced in step (f) to a unit operating under typical conditions of primary reform of the industrial steam reform process to allow the conversion of methane to CO, CO2 and H2; h) treat the gas mixture produced in step (g) using conditions typical of the shift stage of the industrial steam reforming process, to allow the conversion of carbon monoxide CO2 and hydrogen; i) purify the hydrogen produced from the shift reactor, using methods used in the industrial process of steam reform. 2- PROCESS, according to claim 1, characterized in that said ethanol charge comprises anhydrous ethanol, hydrated ethanol or, preferably, raw ethanol. 3- PROCESS, according to claim 1, characterized in that said hydrogen feed comprises the recycling of the product obtained in said ethanol conversion. 4- PROCESS, according to claim 1, characterized in that said nickel oxide is present in the catalyst with a content in the range between 12% w / w and 20% w / w. 5- PROCESS, according to claims 1 and 4, characterized in that said alkali metal promoting element comprises potassium, present in the catalyst with a content between 1% w / w and 3% w / w. 6- PROCESS, according to claim 1, characterized in that said catalyst comprises a second metallic element, of the group of noble metals, particularly Pt and Pd, present in the catalyst with a content of less than 0.5% w / w, in relation to to the Ni metal content, in order to favor the reduction of the metal oxide species in the temperature range between 350 ° C and 550 ° C. 7 - PROCESS, according to claim 6, characterized in that the second metallic element, present in the catalyst has a content less than 0.1% w / w, in relation to the metallic Ni content. 8. PROCESS, according to claim 1, characterized in that said catalytic system comprises a nickel oxide catalyst on a support selected from the group of alkali metal titanates. 9. PROCESS, according to claims 1 and 8, characterized in that said support comprises calcium titanate.